Apparatus for making carbon electrodes or neutronic reactor core bars



g- 23, 1966 H. JUEL ETAL 2 APPARATUS FOR MAKING CARBON ELECT ES OR NEUIC REACTOR CORE BAR Original Filed Feb 9, 1961 2 Sheets-Sheet l H" ii 1mi M 3, 1966 L. H. JUEL ETAL 3,267,518

APPARATUS FOR MAKING CARBON ECTRODES OR NEUTRONIC REACTOR G0 BARSOriginal Filed Feb. 9, 1961 2 Sheets-Sheet 2 United States Patent3,267,518 APPARATUS FOR MAKING CARBGN ELEC- TROgES OR NEUTRONIC REACTGRCURE BAR Leslie H. Joel and Bruce L. Bailey, Lewiston, N.Y., assignorsto Great Lakes Carbon (Importation, New York, N.Y., a corporation ofDelaware Original application Feb, 9, 1961, Ser. No. 88,064. Divided andthis application Dec. 27, 1963, Ser. No. 337,970

9 Claims. (Cl. 18-12) This invention relates primarily to the productionof a special type of carbonaceous electrode or core material bar foratomic reactors, said bars, when graphitized, and properly placed in aneutronic reactor core providing a maximum stability and minimumsusceptibility to high temperature radiation damage. The invention isparticularly related to special apparatus adapted for making such corematerial bars. The present application is a division of our co-pendingapplication, Serial Number 88,064, tfiled February 9, 1961.

The rods or bars being referred to, which will generally besubstantially rectangular in cross section, are used to perform thefunction of rods or blocks such as those shown and depicted by thenumber 77 in FIGURE 22 of the Fermi et al. Patent 2,708,656.

In the design of the reactors of this patent, and of similar reactors,the problem is encountered wherein excessive shrinkage vertically acrossa series of blocks 77 resulting from high temperature radiation damage,causes a downward slumping of the whole reactor core assembly therebypreventing certain mechanical operations essential to the properfunctioning of the reactor and necessitating relatively frequentreconstruction or repair thereof. Radiation effects or damagehorizontally across a series of blocks 77, or along the length of blocks77, do not occasion as serious problems. Thus, it is advantageous if theblocks 77, can be so constructed that they will have a controllable andpredictable response to high temperature radiation damage with a minimalshrinkage in the one critical direction (the vertical direction in thisinstance). This result obtains when the highly anisotropic graphitecrystallites in the bars or blocks are mutually oriented in a mannerapproaching that characteristic of a single crystal of natural or flakegraphite. Such bars under exposure to high temperature radiation wouldsuffer minimal shrinkage in the direction perpendicular to the planes ofthe graphite crystallites. By controlling the internal orientation ofthese graphite crystallites or coke or carbonaceous particles employedin the manufacture of these rods and combining this with properplacement of such internally oriented rods in the reactor, after saidrods or blocks have been grap'hitized, the deleterious radiation effects'fiO'lH the uranium rods 75 are dispelled horizontally across a seriesof such rods or in a direction along the length of the rods rather thanvertically, thereby minimizing downward slumping. The susceptibility ofthese core material bars to high temperature radiation damage in the onecritical direction is thereby very greatly minimized with the resultthat the frequentness of reconstruction or repair of the reactor isgreatly lessened.

T his invention is directed toward the discovery and control of thoseconditions effectuating the best internal structure of such rods, bestreactor placement of such rods, the formulation and processing forbringing about such controlled orientation and placement, and also withthe discovery, design and construction of special extrusion apparatuswhich will mechanically assist in bringing about this orientation.

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We have found that the core material rods best suited for use inneutronic reactors and as depicted in FIGURE 5 should essentially becomprised, when in their extruded green state, of carbonaceous particlesin substantially platelet form, wherein said platelets, when extruded inthe apparatus of this invention, form lamellae lengthwise of the rod.These lamellae are disposed in a plurality of superimposed planes a highpercentage of which planes are substantially mutually parallel. Thispreferential orientation or alignment of the lamellae or plateletsobtains in a green extruded bar, when after baking and graphitizing saidgreen bar, the physical properties, e.g., Coefficient of ThermalExpansion, Resistivity, etc. measured along three mutually perpendicularaxes corresponding to the two edges and length of a bar of rectangularcross section exhibit approximately the same type of anisotropycharacteristic of a single crystal of graphite. In other words, themagnitude of any given property measured along the axes of extrusion andin one direction, e.-g., along the width perpendicular to the extrusionaxis, will be substantially different from the magnitude of that sameproperty measured in the direction (i.e., along the height) mutuallyperpendicular to the other two axes. These effects and their meaningwill be made clearer by reference to the example-s which follow.

We have also lfound that all of the rods in the neut-ronic reactorshould be so placed that these lamellar planes are substantiallyhorizontal throughout the entire reactor. This can be better understoodby referring to said FIG- URE 5 wherein a perspective view of a portionof a typical neutronic reactor is shown and wherein bars or rods 20 intheir extruded green, viz. termed, but unbaked condition having lamellae'22 disposed in a .plurality of superimposed parallel planes are shown,and also wherein all of the rods of the reactor are properly placed withrespect to each other. The cylindrically shaped holes 21 are centrallylocated within each of the rods or bars to accommodate fuel elements.(It is to be understood that the rods will be graphitized before theirplacement in the reactor with the green state orientation abovedescribed for illustrative purposes preserved.) When these conditionsprevail, the CTE (coefficient of thermal expansion) and resistivity ofthe rods when graphitized are considerably greater in the X directionthan they are in the Y or Z directions. This results in the minimizationof radiation damage in the X direction and the substantial reduction ofdownward slumping caused thereby when such graphitized rods or bars areused in the reactors. As previously stated, the elimination orminimization of damage caused in the horizontal or Z direction, orlengthwise of the rods or in the Y direction, is not nearly so criticalto the proper continued functioning or the reactor as is theminimization of damage in the vertical or X direction. This is becausethe base of the reactor remains substantially [firm and mechanicallysound even with damage in these directions, whereas slumping in the Xdirection soon creates mechanical in'operability and damage throughoutthe entire reactor.

We have also discovered extrusion apparatus which is ideally equipped orconstructed to bring about the production of such bars or rods havingthe orientation properties described, such apparatus and modificationsthereof being shown in FIGURES 1 through 4.

FIGURE 1 is a sectional view of the extrusion device taken on the line11 of FIGURE 2.

FIGURE 2 is a vertical sectional view of the extrusion device, taken onthe line 22 of FIGURE 1.

FIGURE 3 is a plan sectional of the device taken on the line 33 ofFIGURE 2.

FIGURE 4 is a fragmentary vertical sectional view of the device in amodified form.

The apparatus in its most generally used form is comprised of threeseparate, diflerently shaped sections. These include a cylindricalextrusion chamber 1, a transition section 2, and a final forming section3. The transition section has a circular inlet 4 and a substantiallyrectangular outlet 5. As is best illustrated by FIGURES 1 and 2, one ofthe dimensions or the height of said rectangular outlet 5 issubstantially less than the diameter of the circular inlet 4. The widthor breadth or the other dimension of rectangular outlet 5, on the otherhand, is at least approximately equal to the diameter of the inlet andpreferably is substantially greater than the diameter of circular inlet4. FIGURE 2 shows the reduction which takes place in the transitionsection while FIGURE 3 shows the preferred enlargement. The transitionsection 2 is so designed and constructed as to smoothly and graduallychange the cross section of the mixture being extruded from circular tosubstantially rectangular, and to bring the material being extruded toone of the final dimensions desired for the products in their greenstate. As a consequence of this, it is preferred that the crosssectionalarea of the mass as it proceeds through this section be relativelyconstant, although this is not absolutely essential for the attainmentof bodies having improved properties. This transition or second section2 leads into a final forming or third section 3, the substantiallyrectangular inlet of which is the same as (and therefore has thedimensions of) the substantially rectangular outlet of the second ortransition section. The final forming or third section also has asubstantially rectangular outlet 6, the breadth of which issubstantially the same as or equal to the breadth of .the inlet, but theother dimension of which, viz. height, is substantially less than itscorresponding dimension at the inlet. This one substantially equaldimension of the inlet and outlet of the third or final forming sectionis due to the fact that the third or final forming section possesses twosubstantially parallel walls 7 and 8 so that one of the dimensions ofthe mass being extruded remains substantially constant as it passestherethrough. The final forming or third section 3 also possesses twoconverging Walls 9 and 10 which compress the extrudable carbonaceousmixture, which will be described in more detail hereinafter, as itpasses therebetween from the transition or second section 2. Theconverging walls 9 and 10 preferably merge with the walls of thetransitional second section in a somewhat curving manner therebyminimizing or preventing any sharply angular areas. These convergingwalls are also generally curved in a manner whereby they define acontinuously diminishing thickness of the material passing therebetweenfor a portion thereof, most generally by means of curved walls havingcontinuously diminishing slope, after which these walls also becomesubstantially parallel to each other.

In a specific and preferred form of the invention, a blade like vane 11is provided near the entrance of the final forming or third section.Typically it extends between the parallel walls thereof and isperpendicular thereto and is approximately equidistant from theconverging walls. The vane may also possess flanges by means of which itcan be mounted in recesses or slots in the parallel walls of theapparatus. This vane 11 acts in conjunction with the curvature of thewalls to assist in setting up shear forces in the mixture being extrudedas it passes adjacent thereto and these forces tend to align theplatelet-like particles of the carbonaceous mixture in planes parallelto the vane and to the axis of the apparatus and perpendicular to theparallel walls of the final forming or third section. These shearforces, in addition to the shear forces exerted upon and set up in theextrudable mixture as it passes through the transition section and as itis compressed in passing between the converging and parallel walls ofthe final forming or third section act together to form an extruded,green, substantially rectangular cross-sectioned carbon rod wherein theplatelet-like particles of the carbonaceous mixture in their extrudedcondition align to comprise lamellae, sometimes somewhat discontinuousin nature and at other times very nearly continuous, disposed in aplurality of superimposed planes a high percentage of which saidlamellar planes are substantially mutually parallel and approximatelyperpendicular to the parallel walls of the third or final formingsection. It should be understood that in many cases such a vane may notbe required and that a device such as shown in FIGURE 1 is sufficient toobtain the required degree of orientation. Its need is also somewhatdependent on the amount of transition taking place in the transition orsecond section, and converging in the third section, etc.

It should also be appreciated that it is sometimes undesirable orunnecessary to employ a cylindrical extrusion chamber before thetransition section. Such a case may occur where it is desired to employmeans other than a cylindrical extrusion chamber to introduce thecarbonaceous mass into the transition section. Because most of thedesired orientation of the platelet-like particles is obtained bypassing a proper extrudable mixture through the transition section andthe final forming section even without employing a cylindrical firstsection, the combination of just these two sections is also claimed. Theemployment of such a first section, however, is preferred.

It should also be appreciated that more than one vane may be employednear the inlet of the final forming section or near the outlet of thetransition section, depending somewhat on the size of the inlet of thefinal forming section. The employment of one or more vanes or bladelikemembers 11 and the particular placing of same and configuration of saidmembers selected are all variables which may depend on thecharacteristics of the mix being extruded, temperatures and pressuresemployed, etc. They will of course be so chosen and designed as toobtain a maximum amount of orientation of the platelet-like particles,consistent with minimum counter pressures, good production rates andabsence of any cleavage lines in the final, extruded but unbaked, greenproduct.

In assembling the extrusion device of the present invention, the generalprocedure is to first assemble the final forming section which generallyis formed from two correspondingly shaped members. The inlet end of thefinal forming section possesses a flange 15. The outlet end of thetransition section also possesses a flange 16. Each of these flangespossess a number of corresponding holes 31 so that the flanges may becoupled to one another by any conventional means 32 such as nuts andbolts inserted therethrough, or threaded .therein. Before the finalforming and transition sections are coupled together however it isgenerally the practice to insert one or more vanes 11 having flangesinto position in either the final forming section or in the transitionsection or partly in each. This is generally accomplished by sliding theflanges of said vane or vanes into slots in the walls of these sections.The entry portion 34 of the transition zone may typically possessexternal threads for engagement with internal threads in a cylindricalextrusion member 1 in those instances where a cylindrical extrusionmember is employed. The general procedure, therefore, is to coupletogether corresponding sections of the final forming section, insert avane or blade 11 in slots of the walls thereof, bolt flange 16 oftransition section 2 to flange 15 of the final forming section 3 andthen thread a cylindrical extrusion member 1 onto the entry end of thetransition section.

Eye-bolts may be threaded into one or more of the sections in order toprovide convenient means for lifting and locating the device. Acircumferential heating chamber may surround the device such as at theentry portion of the final forming section in order to assist in keepingthe extrudable carbonaceous mass at an optimum fluidity level forobtaining maximum particle orientation. Steam or other heat transfermeans may be employed in this region. The cylindrical extrusion memberand the tram sition seciton may also be provided with or surrounded byheating means in order to keep the mass being extruded at an optimumfluidity or viscosity.

Although the apparatus will generally be comprised of or assembled fromtwo or three separate and distinct, differently shaped sections, itshould be understood that this segmentation is or may not be strictlynecessary and that such sections may exist in a singly fabricated apparatus having the different geometrically shaped chambers previouslydescribed.

Conventional extrusion techniques for making electrodes generallycomprise passing a pitch-carbonaceous mixture from a mud chamber througha cylindrical extrusion die such as depicted as 1 in FIGURE 2. Thecylindrical rods fabricated by such equipment are of course entirelyunsuitable for use in nuclear reactors in the manner discussedpreviously. Not only do they not possess the proper geometricalcross-section, but also, even if a substantially square or rectangularcross-sectioned product were fashioned from such cylindrically shapedstarting pieces, such as by machining off four arcs from the outerperiphery, such a product would not possess the orientation propertiesrequired to minimize susceptibility to radiation damage in nuclearreacators. This is because the platelet-like particles would tend toalign themselves in concentric ring fashion lengthwise of the products.Not only would such products lack the desired orientation but even ifthey possessed same, they would be unduly expensive and impracticalbecause of the amount of machining that would be necessary to transformthem into substantially square or rectangular crosssectioned productsand also because of loss of materials involved.

Direct extrusion into products such as rods or slabs which are square orrectangular in cross-section by means of conventional extrusion devices,not having the characteristics of the apparatus of this invention, alsoresult in rods lacking the desired orientation. This is primarilybecause such devices are not characterized by a die having twosubstantially parallel Walls, but instead utilize dies having two pairof converging opposite walls. Such devices also lack transition sectionssuch as previously characterized. All of these factors prevent theobtainment of the desired preferential orientation such as is achievedwhen utilizing the apparatus of this invention.

Some of the apparatus combinations of this invention are, however,designed to utilize cylindrically shaped, conventional extrusion diesand further, without waste or machining, to transform carbonaceousmixtures which have been acted upon by such extrusion dies into carbonproducts having the desired rectangular cross-section and also thedesired particle orientation. In order to accomplish the foregoing theapparatus combinations of the present invention which possess or utilizesuch cylindrically shaped sections also comprise or possess thetransition section 2 which possesses a circular inlet 4 and asubstantially rectangular outlet 5, the circular inlet having the samecross section as the outlet of the cylindrical extrusion member 1. Thetransition piece 2 is also preferably so designed that the extrudablemixture passing therethrough is caused to be substantially compressed inone dimension and allowed or caused to substantially expand in adimension normal thereto. This relationship applies to the transitionsection shown in FIGURES 2 and 3. The cross-sectional area of themixture being extruded at any given point in the transition section ofthese figures is relatively constant to insure that the simultaneousdimensional compression and expansion of the mixture as it is passingtherethrough is relatively uniform.

When the transition piece or section in its preferred from has reachedthe final larger (and expanded) dimension desired for the mass beingextruded, this section ends and the mixture being extruded enters into afinal forming or third section whose larger dimension is substantiallythe same both at the entry and exit 01 said section, but whose smallerdimension at the entry is uniformly diminished by two Walls whichconverge toward each other until they have compressed the mass beingextruded into the desired substantially rectangular cross-sectionalshape. This rectangular cross-sectioned extruded slab or block may then,if desired, be cut lengthwise into rods such as shown in FIGURE 5, whichare substantially square in cross-section. Or the product may sometimesbe used as is.

As shown in the drawings, the larger dimension of the mass beingextruded remains constant in the final forming section while the smallerdimension is substantially further reduced therein, and a product,therefore, having the desired orientation is produced. Also, the outletfrom the transition section and the inlet of the final forming sectionare of the same cross-section and are substantially rectangular shaped,One dimension of this rectangle is substantially greater than the otherdimension. In the final forming section, the lesser dimension is reducedwhile the larger dimension remains constant. This larger dimension, aspreviously stated, is at least equal to the diameter of the circularinlet of the transition section and preferably enlarged thereover. Theserelationships are necessary in order to insure complete and uniformtransition from a circular cross section to a rectangular cross sectionin the transition section, and the subsequent diminishing in properamount of the smaller dimension of the extrudable mixture while itslarger dimension remains constant as the extrudable mixture passesthrough the final forming or third section bringing about the desiredpreferential orientation of the platelet particles present in thecarbonaceous mixture being extruded.

While we have been generally referring to transition sections havinginlets or entrances which are circular in cross-section, it should beunderstood that the invention is not limited to this configurationexcept when a cylindrical extrusioin member 1 is employed in conjunctionwith the transition section. As previously stated, this is not alwaysthe case. The important feature of the transition section is that itsoutlet 5 shoud be substantially rectangular with one dimensionsubstantially greater than its other. It is also necessary that only onedimension of the mass passing therethrough be reduced, and preferablethat the other dimension be increased. But while the inlet of thetransition section is preferably circular in crosssection, it may alsobe square, hexagonal, octagonal or of any regular cross-section such asmay be inscribed by a circle. In other words, it can be of any regulargeometrical shape which can be inscribed by a circle, ranging generallyfrom a square to a circle itself. The diameter of an inscribed circlethen always approximates the distance of a line drawn between oppositesides and through the center of said inlet.

The following examples are set forth in order to more fully describe theinvention.

Example 1 An extrudable carbonaceous mass was prepared from a mixture ofapproximately 37 parts of coal tar pitch binder and parts of needle cokesuch as shown in US. Patent 2,775,549. The particles of needle coke wereof such a size that at least 55% passed through a 200 mesh screen andsubstantially all passed through a 20 mesh screen. This extrudablemixture was mixed at a temperature of approximately C., cooled toapproximately 100 C., and then extruded through the apparatus shown inFIGURES 1-3. The platelet like carbonaceous particles of this mixtureafter their passage through the apparatus were orientated in lamellaedisposed in a plurality of superimposed planes a high percentage ofwhich planes were substantially mutually parallel and approximatelyperpendicular to the substantially parallel walls of the third or finalforming section. The ratio of the height of the inlet of this finalforming section to the height of the outlet of said section was about 2to 1. In other words, the smaller dimension of the extrudable masschanged by this amount while the larger dimension remained substantiallyconstant. The extruded green carbon product was substantiallyrectangular in cross-section and possessed the platelet orientationpreviously described. This green carbon product was baked andgraphitized in accordance with conventional techniques and was then,except for lengthwise cutting and final machining and boring, ready forplacement and use in neutronic reactors also as previously described.

Example 2 The procedure of Example 1 was repeated employingapproximately 40 parts of pitch binder and 100 parts of needle coke ofsuch a particle size that at least 55% passed through a 200 mesh screenand substantially all passed through a 20 mesh screen. This mixture wasextruded through the apparatus shown in FIGURES 1-3. The green carbonproduct produced, when baked and graphitized, possessed a CTE (1/ C. of12.8 in the Z direction, 39.4 in the X direction and 10.7 in the Ydirection, as these directions are indicated in FIGURE 5. It can be seenfrom this that the magnitude of the CTE along the axis of extrusion andalong the width perpendicular to the extrusion axis are substantiallydifferent from the magnitude of the CTE measured along the X directionor the height of the rod, which is mutually perpendicular to the othertwo directions. The resistivity (ohm/in. 10 of this product was 34 inthe Z di' rection, 65 in the X direction and 29 in the Y direction.

Example 3 The procedure of Example 1 was repeated employingapproximately 43 parts of pitch binder and 100 parts of needle coke ofsuch a size that at least 55% passed through a 200 mesh screen andsubstantially all passed through a mesh screen. The mixture was extrudedthrough the cylindrical extrusion chamber and transition sections ofFIGURES 1-3, but using the modified die shown in FIGURE 4. The greencarbon product produced when baked and graphitized possessed a CT E inthe Z direction of 16.2, a CTE of 53.5 in the X direction and a CTE of11.2 in the Y direction. The resistivity of this product was 33 in the Zdirection, 83 in the X direction and 33 in the Y direction.

The desired preferential orientation obtained in the foregoing examplesis not achieved, nor is it achievable when using a standard type ofextrusion apparatus.

It will be appreciated from the foregoing description and examples thata wide variation in the processing conditions, starting materials andapparatus features are possible and contemplated when carrying out thepractices of this invention. For example, resins or suitable hydrocarbonbinders may be employed as well as pitch. The amount of binder employedand the particle sizes and types of starting carbonaceous platelets mayall be varied. Carbonaceous particles in substantially platelet formsuch as finely ground (preferably all at least finer than 20 mesh)needle coke shown in U.S. Patent 2,775,549, decomposed silicon carbide,natural graphite and kish and mixtures thereof are among those which maybe employed as starting carbonaceous materials and mixed with a bindersuch as pitch and processed and extruded through the devices of thepresent invention to form products having the desired properties. Theamount of pitch used when it is employed as a binder will generally varyfrom about to about parts per 100 parts of carbonaceous material. Thetemperatures and pressures employed may be varied. The use of acylindrical extrusion chamber is optional and if it is used, it may havea variable length. The transition section may vary in its angle of slopeand in its length as well as in other manners previously described. Thesize of the inlet of the final forming section may be varied greatly andthe ratio of the dimension of the inlet of the final forming sectionwhich is compressed to its reduced dimension at the outlet may varyconsiderably, such as from about 2:1 to 5:1 with suitable modificationin the contour of the final forming section. The employment of one ormore vanes in conjunction with all of the foregoing variables and thepossible varied locations of same all taken together make it possible toform products having the desired characteristics previously describedand are contemplated as being embraced in the present invention. Thesevariations, the selection of the desired starting mate rials, equipmentemployed, etc., are considered within the skill of one working in theart once the main features of this invention are before him. Wetherefore do not wish to be limited except as defined by the appendedclaims.

We claim:

1. An apparatus suitable for acting upon an extrudable material andcausing preferential orientation therein while it is being extrudedcomprising in combination a forming 7 zone consisting of a transitionsection having an inlet which is substantially inscribable by a circleand a substantially rectangular outlet one dimension of which issubstantially less than the diameter of the inlet and the otherdimension of which is substantially greater than the diameter of theinlet, and a final forming section having a substantially rectangularinlet whose dimensions are the same as the outlet of the transitionsection and a substantially rectangular outlet the larger dimension ofwhich is substantially the same as and corresponds to the largerdimension of the inlet, and the smaller dimension of which issubstantially less than the smaller dimension of said inlet, said finalforming section having two substantially parallel walls and two wallswhich converge for a portion of their length and which are adapted tocompress a mass as it passes therethrough from the transition section.

2. An apparatus suitable for acting upon an extrudable material andcausing preferential orientation therein while it is being extrudedcomprising in combination a forming zone consisting of a transitionsection having a circular inlet and a substantially rectangular outletone dimension of which is substantially less than the diameter of theinlet and the other dimension of which is substantially greater than thediameter of the inlet, and a final forming section having asubstantially rectangular inlet whose dimensions are the same as theoutlet of the transition section and a substantially rectangular outletthe larger dimension of which is substantially the same as andcorresponds to the larger dimension of the inlet, and the smallerdimension of which is substantially less than the smaller dimension ofsaid inlet, said final forming section having two substantially parallelwalls and two walls which convergefor a portion of their length andwhich are adapted to compress a mass as it passes therethrough from thetransition section.

3. An apparatus suitable for acting upon an extrudable material andcausing preferential orientation therein while it is being extrudedcomprising in combination a forming zone consisting of a cylindricallyshaped extrusion section, a transition section having a circular inletand a substantially rectangular outlet, one dimension of saidrectangular outlet being substantially less than the diameter of thecircular inlet and the other dimension of the rectangular outlet beingsubstantially greater than the diameter of the circularinlet, and afinal forming section having a substantially rectangular inlet whosedimensions are the same as the outlet of the transition section and asubstantially rectangular outlet the larger dimension of which issubstantially the same as and corresponds to the larger dimen sion ofthe inlet, and the smaller dimension of which is substantially less thanthe smaller dimension of said inlet, said final forming section havingtwo substantially parallel walls and two walls which converge for aportion of their length and which are adapted to compress a mass as itpasses therethrough from the transition section.

4. An apparatus according to claim 1 having at least one bladelike vanenear the entrance of the final forming section suitably positioned toassist in giving the orientation desired in the mass being extruded.

5. An apparatus suitable for acting upon an extrudable material andcausing preferential orientation therein while it is being extrudedcomprising in combination a forming zone consisting of a cylindricallyshaped extrusion section, a transition section having a circular inletand a substantially rectangular outlet, the width of said rectangularoutlet being substantially greater than the diameter of the circularinlet and the height of the rectangular outlet being substantially lessthan the diameter of the circular inlet, and a final forming sectionhaving a substantially rectangular inlet whose dimensions are the sameas the outlet of the transition section and a substantially rectangularoutlet whose width is substantially the same as the width of the inlet,and whose height is substantially less than the height of said inlet,said final forming section having two substantially parallel walls andtwo walls which converge for a portion of their length and which areadapted to compress a mass as it passes therethrough from the transitionsection.

6. An apparatus suitable for acting upon an extrudable material andcausing preferential orientation therein while it is being extrudedcomprising in combination a forming zone consisting of a transitionsection having an inlet which is substantially inscribable by a circleand a substantially rectangular outlet one dimension of which issubstantially less than the diameter of the inlet and the otherdimension of which is at least equal to the diameter of the inlet, and afinal forming section having a substantially rectangular inlet whosedimensions are the same as the outlet of the transition section and asubstantially rectangular outlet the larger dimension of which issubstantially the same as and corresponds to the larger dimension of theinlet, and the smaller dimension of which is substantially less than thesmaller dimension of said inlet, said final forming section having twosubstantially parallel walls and two walls which converge for a portionof their length and which are adapted to compress a mass as it passestherethrough from the transition section.

7. An apparatus suitable for acting upon an extrudable material andcausing preferential orientation therein while it is being extrudedcomprising in combination a forming zone consisting of a transitionsection having a circular inlet and a substantially rectangular outletone dimension of which is substantially less than the diameter of theinlet and the other dimension of which is at least equal to the diameterof the inlet, and a final forming section having a substantiallyrectangular inlet whose dimensions are the same as the outlet of thetransition section and a substantially rectangular outlet the largerdimension of which is substantially the same as and corresponds to thelarge dimension of the inlet, and the smaller dimension of which issubstantially less than the smaller dimension of said inlet, said finalforming section having two substantially parallel walls and two wallswhich converge for a portion of their length and which are adapted tocompress a mass as it passes therethrough from the transition section.

8. An apparatus suitable for acting upon an extrudable material andcausing preferential orientation therein while it is being extrudedcomprising in combination a forming zone consisting of a cylindricallyshaped extrusion section, a transition section having a circular inletand a substantially rectangular outlet, one dimension of saidrectangular outlet being substantially less than the diameter of thecircular inlet and the other dimension of the rectangular outlet beingat least equal to the diameter of the circular inlet, and a finalforming section having a substantially rectangular inlet whose dimenionsare the same as the outlet of the transition section and a substantiallyrectangular outlet the larger dimension of which is substantially thesame as and corresponds to the larger dimension of the inlet, and thesmaller dimension of which is substantially less than the smallerdimension of said inlet, said final forming section having twosubstantially parallel walls and two walls which converge for a portionof their length and which are adapted to compress a mass as it passestherethrough from the transition section.

9. An apparatus according to claim 6 having at least one bladelike vanenear the entrance of the final forming section suitably positioned toassist in giving the orientation desired in the mass being extruded.

References Cited by the Examiner UNITED STATES PATENTS Re. 25,570 5/1964Lemelson 2517 X 1,245,898 11/1917 Gates 1812 1,411,170 3/1922 Kahr 25-171,952,038 3/1934 Fischer. 2,126,869 8/1938 Burchenal et a1. 2,168,2888/1939 Fischer 1812 X 2,402,281 6/1946 Green 18-12 X 2,572,677 10/1951Tench 18-12 2,715,256 8/1955 Siegrist 1812 X 2,817,113 12/1957 Fields18-12 X WILLAM I. STEPHENSON, Primary Examiner. ROBERT F. WHITE, I.SPENCER OVERHOLSER, Examiners.

J. A. FINLAYSON, JR., L. S. SQUIRES,

Assistant Examiners.

6. AN APPARATUS SUITABLE FOR ACTING UPON AN EXTRUDABLE MATERIAL ANDCAUSING PREFERENTIAL ORIENTATION THEREIN WHILE IT IS BEING EXTRUDEDCOMPRISING A COMBINATION A FORMING ZONE CONSISTING OF A TRANSITIONSECTION HAVING AN INLET WHICH IS SUBSTANTIALLY INSCRIBALE BY A CIRCLEAND A SUBSTANTIALLY RECTANGULAR OULET ONE DIMENSION OF WHICH ASUBSTANTIALLY LESS THAN THE DIAMETER OF THE INLET AND THE OTHERDIMENSION OF WHICH IS AT LEAST EQUAL TO THE DIAMETER OF THEINLET, AND AFINAL FORMING SECTION HAVING A SUBSTANTIALLY RECTANGULAR INLET WHOSEDIMENSIONS ARE THE SAME AS THE OULET OF THE TRANSITION SECTION AND ASUBSTANTIALLY RECTANGULAR OULET THE LARGER DIMENSION OF WHICH ISSUBSTNATIALLY THE SAME AS AND CORRESPONDS TO THE LARGER DIMENSION OF THEINLET, AND THE SMALLER DIMENSION OF WHICH IS SUBSTANTIALLY LESS THAN THESMALLER DIMENSION OF SAID INLET, SAID FINAL FORMING SECTION HAVING TWOSUBSTANTIALLY PARALLEL WALLS AND TWO WALLS WHICH CONVERGE FOR A PORTIONOF THEIR LENGTH AND WHICH ARE ADAPTED TO COMPRESS A MASS AS IT PASSESTHERETHROUGH FROM THE TRANSITION SECTION.